// set Variable
var agent = navigator.userAgent;
if (navigator.appVersion.indexOf('Mac') > 1) {
  document.write('<link rel="stylesheet" type="text/css" href="css/mac.css" media="screen">');
} else {
  document.write('<link rel="stylesheet" type="text/css" href="css/win.css" media="screen">');
}

// for debug
/*
alert(flag);
*/